Zeolite graphic. Computer graphic of a crystal of zeolite, a mineral used as a catalyst, for absorbing gases, drying solvents and for removing molecules of a certain size (a molecular sieve). Ions are shown as red spheres whilst inter-ionic bonds are shown as lines. Zeolites consist of a negatively-charged framework of aluminium, silicon and oxygen which surround positively-charged ions in the cavities. The properties of zeolite arise because its framework structure creates channels through which molecules may be drawn into the crystal. Image of a zeolite crystal looking along its vertical axis or c-axis.